i found easy way to power fans at 9v earlyer, makes them nice and quiet, doesnt cost much atall, and is very simple to make. (airflow/niose will be reduced about 25% by this - 25% will not make too much differnece on niose though due to the logarithmic scale its measured on

multimeter (optional)
soldering iron (optional, but its better if you have one)
scissors/teeth (to cut wire)

parts: (maplin is the site im going to get links from , farnel or another shop may be a lot cheaper!)
heatsink - maplin have some but i use cut up cpu ones, there better and i have some spare anyway...
wire - any wire will do, as long as it can carry 2 amps or the current used by what you wil be powering.
strip board - to mount it on. if you havent got any then just get a piece of plastic and make some holes in it. stip board is nicer though.
connectors - maplin sell hdd style ones and there may be cheaper places that i dont know of..

if you look at the datasheet for the L78S09CV it has soem info on it. ignore most of it as the most simple design to do it isnt on there, afaik it will have about the same result.

if you look on the top pic on the datasheet (TO-220 case), the leftmost leg is the input, this is where you need to connet your +12v. the middle pin is ground, this goes to ground on your psu. the last pin is output, +9v.
also note that the metal back part of the case is usually conencted to one of the legs, i forget which, but usually ground or output. this means it cant be mounted directly onto your pc's case, or, what i inteded to do, was mount it onto a ALU floppy bay cover. to do this you would have to use a thermal pad that isnt conductive of electrisity. the capacitors shown in the diagrams arnt needed. you can just conect the pins to wiires as above - you dont even need a board to mount it on, just solder the wires to the legs.
connect two wires to ground - ones for going back to pc, and the other is for powering any load (voltage is potential difference, and without a ground there would be nowhere for current to flow, which means we have 0v! you could use your pc's 12v as + and the 9v from this as -, giving 3v, but thats not recommened, and you have 3.3v from the orange wires on the atx conenctor anyway...).

one of these chips should be able to power a few fans, more than 4x80mm's though isnt recommened (as when motors start, they draw 5x more current than when there running, and the values quoted on back of fans is when there runing)

i am not an electronics expert, but can anyone tell me if its ok to run 2 or 3 of these regulators in parrelel? (to power lots more fans!) they all should have about the same output, so there wounlt have any problems with them
fighting against each other?

i should be able to make these for anyone if there wanted, which might include an ALU floppy bay mount depending on how much time ive got to cut it up...